Mixed finite element methods for linear elasticity with weakly imposed symmetry |
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Authors: | Douglas N. Arnold Richard S. Falk Ragnar Winther. |
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Affiliation: | Institute for Mathematics and its Applications, University of Minnesota, Minneapolis, Minnesota 55455 ; Department of Mathematics, Rutgers University, Piscataway, New Jersey 08854-8019 ; Centre of Mathematics for Applications and Department of Informatics, University of Oslo, P.O. Box 1053, Blindern, 0316 Oslo, Norway |
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Abstract: | In this paper, we construct new finite element methods for the approximation of the equations of linear elasticity in three space dimensions that produce direct approximations to both stresses and displacements. The methods are based on a modified form of the Hellinger-Reissner variational principle that only weakly imposes the symmetry condition on the stresses. Although this approach has been previously used by a number of authors, a key new ingredient here is a constructive derivation of the elasticity complex starting from the de Rham complex. By mimicking this construction in the discrete case, we derive new mixed finite elements for elasticity in a systematic manner from known discretizations of the de Rham complex. These elements appear to be simpler than the ones previously derived. For example, we construct stable discretizations which use only piecewise linear elements to approximate the stress field and piecewise constant functions to approximate the displacement field. |
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Keywords: | Mixed method finite element elasticity |
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